1. Field of the Invention
The present invention relates to a vehicle navigation apparatus and, more particularly, to a vehicle navigation apparatus having a function of searching for facilities located within a surrounding area of a present position of a vehicle when a map image is displayed on a screen of a display device, and a method of searching for and displaying neighborhood facilities using same.
2. Description of the Related Art
A conventional vehicle navigation apparatus is provided with a CPU for controlling the processing associated with navigation, a storage device, such as a CD-ROM or a DVD-ROM, for storing map data, a display device, a global positioning system (GPS) receiver for detecting a present position of a vehicle, a detector, such as a gyro or a vehicle speed sensor, for detecting a present traveling direction and speed of the vehicle, and the like. In such a navigation apparatus, map data including map information regarding the present vehicle position is read from the storage device by the CPU, and based on the map data, a map image covering the present vehicle position and its surroundings is drawn and displayed on a screen of the display device with a vehicle position mark indicative of the present vehicle position superimposed on the screen. The navigation apparatus renders the map image scrollable or the vehicle position mark movable with the map image fixed on the screen as the vehicle travels, thus allowing a user to understand the present traveling situation of the vehicle at a glance.
Generally, the vehicle navigation apparatus has a function of guiding a user or driver to a desired destination (route guidance function) so that the user can easily travel roads to the destination without taking a wrong path. This route guidance function searches for the most appropriate route connecting a starting point (typically, the present vehicle position) to the destination by a simulated calculation, such as the lateral search method or the Dijkstra method, using the map data with the CPU, and the resultant route is stored as a guidance route. The guidance route is displayed on the map image during traveling in such a manner that it is distinguishable from all other roads (for example, by drawing a line in a different color or thickness from that of any other road). Alternatively or additionally, when the vehicle arrives at a predetermined distance from an intersection being approached on the guidance route, an additional guidance map or view of the intersection (an enlarged view of the intersection, an arrow indicative of a direction in which the vehicle is to travel at the intersection, a distance to the intersection, a name of the intersection, or the like) is displayed on the map image being displayed. This function permits the user to understand which road the vehicle is to travel and/or in which direction it is to proceed through the intersection.
While route guidance is being carried out based on such a guidance route function, the route being provided for guidance or the preset destination may often be changed. For example, when the vehicle is intended to stop at a convenience store before reaching the destination initially set, the vehicle navigation apparatus can provide its own “searching function for a neighborhood facility”. When the user previously designates a desired genre of facility of interest for the search, this neighborhood-facility searching function causes the navigation apparatus to search for the designated genre of facility which is located within a predetermined distance from the vehicle position (in this case, the convenience store). Then, the searching function causes the navigation apparatus to display on the screen of the display a list including a name of the facility searched for, a distance and a direction (arrow) from the vehicle position to the facility, or the like. If necessary, the apparatus is further adapted to display on the map image a landmark (brand icon, category icon, or the like) indicative of a position of the facility. In searching for the designated genre of facility, the facility search may often be performed while scrolling the map image as required. Such a neighborhood-facility searching function permits the user to understand a positional relationship between the vehicle position and the designated genre of facility located within a surrounding area of the vehicle position. When a desired facility (landmark) is touched on the screen (or selected by an operation of a remote control unit) as needed, information on this facility can also be obtained.
Such a neighborhood-facility search may also be carried out when the vehicle is stopped before the destination is set, as well as when the vehicle is moving along the guidance route as described above. That is, this search can be performed as needed, as long as the map image is displayed with the vehicle position mark being centered on the display screen.
In the conventional vehicle navigation apparatus, when performing the neighborhood-facility search, an area of a circular or rectangular shape or the like is set that covers a cursor position, which is set on the map image as a center point (the present vehicle position when the map image is not scrolled) and its surroundings. The designated genre of facilities included in the area is displayed in a list.
As a technique associated with the foregoing neighborhood-facility search is proposed a vehicle navigation apparatus having a function of searching for a desired genre of facility located within the surrounding area of the present vehicle position serving as a base point for search (in all directions). This navigation apparatus is designed such that a searching range is enlarged in stages until the number of the search operations reaches a predetermined value, and all facilities searched for are superimposed on the map image and displayed together with the search base point within one screen, as disclosed in JP-A-9-292262, for example.
The neighborhood-facility searching function of the above-mentioned known apparatus enables the user to identify the positional relationship between the vehicle position and the designated genre of facility located within the surrounding area.
Such a navigation apparatus, however, is designed to list and display all facilities which belong to the designated genre and which are located within the surrounding area (in all directions) of the cursor position (or the vehicle position) set as the search base point on the map image, disadvantageously failing to perform search refinement. For example, when the user intends to search for only facilities located in a desired specific direction (e.g. on the west side) viewed from the search base point, the navigation apparatus cannot restrict an object of a searching range to only the facility located to the west of the search base point. That is, even if a genre of a facility of interest to be searched for is designated, the designated genre of the facilities located within a predetermined distance from the search base point in all directions are all listed in the prior apparatus, which results in a relatively large number of facilities being displayed on the screen. If a first list displayed on the screen includes a facility of interest, no problem exists. If not, an additional scroll operation with a scroll button or the like is required for displaying a second or next facility list. This forces the user to repeat the scroll operation until the facility of interest is displayed, which inconveniently becomes burdensome.